Mel Gibson Accuses Ex-Girlfriend of Extortion

Despite a sheriff's investigation into claims that Mel Gibson assaulted ex-girlfriend Oksana Grigorieva, the actor is confident he'll be cleared of any wrongdoing, says a source close to the case.

In fact, he's alleging that it's Grigorieva who broke the law.

According to the source, Gibson will be presenting evidence to detectives that Grigorieva tried to extort money from him and, if he didn't pay, she'd leak recordings of Gibson to the press. He also asserts that she made false claims to the police about his alleged abuse.

Asked about a report Friday that Gibson also allegedly threatened the Russian singer with a gun, L.A. Sheriff's spokesman Steve Whitmore said he could neither "confirm or deny" the allegation. The investigation is ongoing and police say it could take up to a month before prosecutors will be presented a case.

Gibson, 54, and Grigorieva, 40, have been locked in a bitter custody dispute over their 8-month-old daughter, Lucia. Grigorieva alleged in a restraining order filed June 25 that the actor punched her in the face "more than once" on Jan. 6 at his Malibu home, breaking a tooth, knocking out a veneer and causing a concussion.

Sources close to Gibson claim he merely was trying to stop Grigorieva from shaking Lucia "like a ragdoll" and that her accusations are financially motivated.

Grigorieva has reportedly caught Gibson on tape spewing racist comments and hurling other expletives, but a rep for Gibson previously claimed no knowledge of the recordings. "I have no comment on, and furthermore no knowledge of, the credibility or authenticity of any alleged audio tapes," the actor's rep said.